diff --git a/include/mbedtls/cipher.h b/include/mbedtls/cipher.h
index e707808..a1f4738 100644
--- a/include/mbedtls/cipher.h
+++ b/include/mbedtls/cipher.h
@@ -186,6 +186,7 @@
     MBEDTLS_MODE_STREAM,                 /**< The stream cipher mode. */
     MBEDTLS_MODE_CCM,                    /**< The CCM cipher mode. */
     MBEDTLS_MODE_XTS,                    /**< The XTS cipher mode. */
+    MBEDTLS_MODE_CHACHAPOLY,             /**< The ChaCha-Poly cipher mode. */
 } mbedtls_cipher_mode_t;
 
 /** Supported cipher padding types. */